JP2018081204A - Polarization maintaining optical fiber and bidirectional optical transmission device - Google Patents

Polarization maintaining optical fiber and bidirectional optical transmission device Download PDF

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JP2018081204A
JP2018081204A JP2016223444A JP2016223444A JP2018081204A JP 2018081204 A JP2018081204 A JP 2018081204A JP 2016223444 A JP2016223444 A JP 2016223444A JP 2016223444 A JP2016223444 A JP 2016223444A JP 2018081204 A JP2018081204 A JP 2018081204A
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polarization
optical fiber
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一宏 五井
Kazuhiro Goi
一宏 五井
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Fujikura Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
    • G02B6/2793—Controlling polarisation dependent loss, e.g. polarisation insensitivity, reducing the change in polarisation degree of the output light even if the input polarisation state fluctuates
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/126—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind using polarisation effects
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2726—Optical coupling means with polarisation selective and adjusting means in or on light guides, e.g. polarisation means assembled in a light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2726—Optical coupling means with polarisation selective and adjusting means in or on light guides, e.g. polarisation means assembled in a light guide
    • G02B6/2733—Light guides evanescently coupled to polarisation sensitive elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
    • G02B6/2766—Manipulating the plane of polarisation from one input polarisation to another output polarisation, e.g. polarisation rotators, linear to circular polarisation converters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
    • G02B6/2773—Polarisation splitting or combining
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • G02B6/4213—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical elements being polarisation selective optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4216—Packages, e.g. shape, construction, internal or external details incorporating polarisation-maintaining fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4246—Bidirectionally operating package structures
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/0128—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on electro-mechanical, magneto-mechanical, elasto-optic effects
    • G02F1/0131—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on electro-mechanical, magneto-mechanical, elasto-optic effects based on photo-elastic effects, e.g. mechanically induced birefringence
    • G02F1/0134—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on electro-mechanical, magneto-mechanical, elasto-optic effects based on photo-elastic effects, e.g. mechanically induced birefringence in optical waveguides
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2589—Bidirectional transmission

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Abstract

PROBLEM TO BE SOLVED: To make common a constitution in transmitting and receiving units used in a bidirectional optical transmission device.SOLUTION: A bidirectional optical transmission device 10 comprises optical waveguide elements 1a and 1b and a polarization maintaining optical fiber 6 for connecting them to each other. The optical waveguide elements 1a and 1b have substrates 2a and 2b, optical transmitting parts 3a and 3b, optical receiving parts 4a and 4b, and polarization multiplexing/demultiplexing parts 5a and 5b, respectively. An orientation of a slow axis of the polarization maintaining optical fiber 6 relative to the substrate 2a at a connection part to the optical waveguide element 1a and an orientation of a slow axis of the polarization maintaining optical fiber 6 relative to the substrate 2b at a connection part to the optical waveguide element 1b cross nearly orthogonal with each other.SELECTED DRAWING: Figure 1

Description

本発明は、偏波保持光ファイバおよび双方向光伝送装置に関する。   The present invention relates to a polarization maintaining optical fiber and a bidirectional optical transmission apparatus.

従来から、下記特許文献１に示されるような双方向光伝送装置が知られている。この双方向光伝送装置は、第１の送受信ユニットと、第２の送受信ユニットと、偏波保持光ファイバと、を備える。第１の送受信ユニットは、第１の光送信部と、第１の光受信部と、第１の偏波合分波部と、を有する。第１の偏波合分波部は、第１の光送信部及び第１の光受信部に接続され、異なる偏波状態の光波を分波および合波する。第２の送受信ユニットは、第２の光送信部と、第２の光受信部と、第２の偏波合分波部と、を有する。第２の偏波合分波部は、第２の光送信部及び第２の光受信部に接続され、異なる偏波状態の光波を分波および合波する。偏波保持光ファイバは、第１の偏波合分波部と第２の偏波合分波部とを接続する。
この双方向光伝送装置では、１本の偏波保持光ファイバ内を双方向に通過する２つの光波の電界面の向きを互いに直交させることが開示されている。また、このように１本の偏波保持光ファイバ内を通過する２つの光波の電界面の向きを互いに直交させるために、第１の光送信部と、第２の光送信部と、は電界面が互いに直交する光波をそれぞれ出射している。このような構成を採用することで、上記２つの光波のクロストークを低減することができる。 Conventionally, a bidirectional optical transmission apparatus as shown in Patent Document 1 below is known. The bidirectional optical transmission device includes a first transmission / reception unit, a second transmission / reception unit, and a polarization maintaining optical fiber. The first transmission / reception unit includes a first optical transmission unit, a first optical reception unit, and a first polarization multiplexing / demultiplexing unit. The first polarization multiplexing / demultiplexing unit is connected to the first optical transmitting unit and the first optical receiving unit, and demultiplexes and multiplexes optical waves in different polarization states. The second transmission / reception unit includes a second optical transmission unit, a second optical reception unit, and a second polarization multiplexing / demultiplexing unit. The second polarization multiplexing / demultiplexing unit is connected to the second optical transmitting unit and the second optical receiving unit, and demultiplexes and multiplexes the optical waves having different polarization states. The polarization maintaining optical fiber connects the first polarization multiplexing / demultiplexing unit and the second polarization multiplexing / demultiplexing unit.
In this bidirectional optical transmission device, it is disclosed that the directions of the electric field planes of two light waves that pass bidirectionally through one polarization-maintaining optical fiber are orthogonal to each other. Further, in order to make the directions of the electric field planes of the two light waves passing through one polarization-maintaining optical fiber orthogonal to each other, the first optical transmitter and the second optical transmitter are electrically connected. Light waves whose interfaces are orthogonal to each other are emitted. By adopting such a configuration, crosstalk between the two light waves can be reduced.

特開昭６２−３２０５号公報JP-A-62-3205

この種の双方向光伝送装置では、送受信ユニットを基板上に配設した光導波路素子を用いる場合がある。上記特許文献１の構成では、第１の光送信部と、第２の光送信部と、が出射する光波の電界面の基板に対する向きが異なっている。同様に、第１の光受信部と、第２の光受信部と、が受信可能な光波の電界面の向きが異なっている。このため、第１の送受信ユニットと、第２の送受信ユニットと、で異なる種類の光導波路素子を用意する必要がある。
このように、種類が異なる２つの送受信ユニットを対にして用いる場合、双方向光伝送装置の製造時のコストアップや、メンテナンス性の低下につながる。 In this type of bidirectional optical transmission apparatus, an optical waveguide element having a transmission / reception unit disposed on a substrate may be used. In the configuration of Patent Document 1, the first optical transmission unit and the second optical transmission unit are different in the direction of the electric field surface of the light wave emitted from the first optical transmission unit with respect to the substrate. Similarly, the direction of the electric field surface of the light wave that can be received by the first optical receiving unit and the second optical receiving unit is different. For this reason, it is necessary to prepare different types of optical waveguide elements for the first transmission / reception unit and the second transmission / reception unit.
As described above, when two transmission / reception units of different types are used as a pair, the production cost of the bidirectional optical transmission apparatus is increased, and the maintainability is reduced.

本発明はこのような事情を考慮してなされたもので、双方向光伝送装置に用いられる一対の送受信ユニットの構成を共通化することを目的とする。   The present invention has been made in view of such circumstances, and an object of the present invention is to share the configuration of a pair of transmission / reception units used in a bidirectional optical transmission apparatus.

上記課題を解決するために、本発明の第１態様に係る双方向光伝送装置は、第１の光送信部と、第１の光受信部と、前記第１の光送信部及び前記第１の光受信部に接続され、異なる偏波状態の光波を分波および合波可能な第１の偏波合分波部と、を有する第１の送受信ユニットが第１の基板上に配設された第１の光導波路素子と、第２の光送信部と、第２の光受信部と、前記第２の光送信部及び前記第２の光受信部に接続され、異なる偏波状態の光波を分波および合波可能な第２の偏波合分波部と、を有する第２の送受信ユニットが第２の基板上に配設された第２の光導波路素子と、前記第１の光導波路素子と前記第２の光導波路素子とを接続する偏波保持光ファイバと、を備え、前記第１の光導波路素子との接続部における前記偏波保持光ファイバの前記第１の基板に対するスロー軸の向きと、前記第２の光導波路素子との接続部における前記偏波保持光ファイバの前記第２の基板に対する前記スロー軸の向きと、が互いに略直交している。   In order to solve the above-described problem, a bidirectional optical transmission apparatus according to a first aspect of the present invention includes a first optical transmission unit, a first optical reception unit, the first optical transmission unit, and the first optical transmission unit. A first transmission / reception unit having a first polarization multiplexing / demultiplexing unit connected to the optical receiving unit and capable of demultiplexing and multiplexing light waves in different polarization states is disposed on the first substrate. The first optical waveguide element, the second optical transmission unit, the second optical reception unit, and the light waves connected to the second optical transmission unit and the second optical reception unit and having different polarization states A second optical waveguide element having a second transmission / reception unit having a second polarization multiplexing / demultiplexing unit capable of demultiplexing and multiplexing the second optical waveguide element, and the first optical waveguide A polarization-maintaining optical fiber that connects the waveguide element and the second optical waveguide element, and the polarization-maintaining light at a connection portion with the first optical waveguide element The orientation of the slow axis of the fiber with respect to the first substrate and the orientation of the slow axis with respect to the second substrate of the polarization maintaining optical fiber at the connection portion with the second optical waveguide element are substantially orthogonal to each other. doing.

上記態様に係る双方向光伝送装置によれば、第１の光導波路素子との接続部における偏波保持光ファイバの第１の基板に対するスロー軸の向きと、第２の光導波路素子との接続部における偏波保持光ファイバの第２の基板に対するスロー軸の向きと、が互いに略直交する。このため、例えば第１の光送信部が横電界（ｔｒａｎｓｖｅｒｓｅ−ｅｌｅｃｔｒｉｃ，ＴＥ）モードの光波を出射すると、第２の光受信部に入射する光波はＴＥモードと直交する横磁界（ｔｒａｎｓｖｅｒｓｅ−ｍａｇｎｅｔｉｃ，ＴＭ）モードとなる。また、第２の光送信部がＴＥモードの光波を出射すると、第１の光受信部に入射する光波はＴＭモードとなる。このように、第１および第２の光送信部が出射する光波の電界面の向きを共通にしつつ、第１および第２の光受信部に入射する光波の電界面の向きを共通にすることができる。これにより、第１および第２の光送信部を共通化し、かつ第１および第２の光受信部を共通化できるため、第１および第２の送受信ユニットの構成を共通化することが可能となる。   According to the bidirectional optical transmission device according to the above aspect, the direction of the slow axis with respect to the first substrate of the polarization maintaining optical fiber at the connection portion with the first optical waveguide element and the connection with the second optical waveguide element The direction of the slow axis with respect to the second substrate of the polarization maintaining optical fiber in the section is substantially orthogonal to each other. For this reason, for example, when the first optical transmission unit emits a transverse-electric (TE) mode light wave, the light wave incident on the second optical reception unit becomes a transverse magnetic field (transverse-magnetic, TM) mode. Further, when the second optical transmission unit emits a TE mode light wave, the light wave incident on the first optical reception unit is in the TM mode. As described above, the direction of the electric field surface of the light wave emitted from the first and second optical transmission units is made common, and the direction of the electric field surface of the light wave incident on the first and second optical reception units is made common. Can do. As a result, the first and second optical transmitters can be shared, and the first and second optical receivers can be shared. Therefore, the configurations of the first and second transmission / reception units can be shared. Become.

また、前記第１の光導波路素子と前記第２の光導波路素子との間で前記偏波保持光ファイバが軸方向にねじられていてもよい。   The polarization maintaining optical fiber may be twisted in the axial direction between the first optical waveguide element and the second optical waveguide element.

この場合、第１の光導波路素子と第２の光導波路素子との間で偏波保持光ファイバがねじられることで、このねじられた部分の前後におけるスロー軸の向きを互いに略直交させることができる。これにより、第１の光導波路素子との接続部における偏波保持光ファイバの第１の基板に対するスロー軸の向きと、第２の光導波路素子との接続部における偏波保持光ファイバの第２の基板に対するスロー軸の向きと、が互いに略直交する構成を、容易に実現することができる。   In this case, when the polarization maintaining optical fiber is twisted between the first optical waveguide element and the second optical waveguide element, the directions of the slow axes before and after the twisted portion can be made substantially orthogonal to each other. it can. Accordingly, the direction of the slow axis of the polarization maintaining optical fiber with respect to the first substrate at the connection portion with the first optical waveguide element and the second direction of the polarization maintaining optical fiber at the connection portion with the second optical waveguide element. It is possible to easily realize a configuration in which the direction of the slow axis with respect to the substrate is substantially orthogonal to each other.

また、前記偏波保持光ファイバは、前記偏波保持光ファイバの一方の端部に配設された、前記光波の電界面の向きを回転可能な偏波回転素子を有し、前記偏波回転素子によって、前記第１の光導波路素子との接続部における前記偏波保持光ファイバの前記第１の基板に対するスロー軸の向きと、前記第２の光導波路素子との接続部における前記偏波保持光ファイバの前記第２の基板に対する前記スロー軸の向きと、が互いに略直交するように構成されていてもよい。   In addition, the polarization maintaining optical fiber includes a polarization rotation element disposed at one end of the polarization maintaining optical fiber and capable of rotating a direction of an electric field surface of the light wave, and the polarization rotation Depending on the element, the direction of the slow axis of the polarization-maintaining optical fiber at the connection with the first optical waveguide element relative to the first substrate and the polarization maintenance at the connection with the second optical waveguide element The direction of the slow axis with respect to the second substrate of the optical fiber may be configured to be substantially orthogonal to each other.

この場合、偏波回転素子が光波の電界面の向きを回転させることで、第１および第２の光送信部が出射する電界面の向きを共通にしつつ、第１および第２の光受信部に入射する光波の電界面の向きを共通にすることができる。これにより、第１および第２の送受信ユニットの構成を共通化することが可能となる。
さらに、このような偏波回転素子を偏波保持光ファイバの一方の端部に設けることにより、偏波回転素子以外の部分には汎用の偏波保持光ファイバを用いて上記態様の双方向光伝送装置を構成することができるため、製造コストを低減してメンテナンス性を向上することが可能となる。 In this case, the polarization rotating element rotates the direction of the electric field surface of the light wave, so that the first and second optical receivers share the same direction of the electric field surface emitted by the first and second optical transmitters. The direction of the electric field surface of the light wave incident on can be made common. This makes it possible to share the configuration of the first and second transmission / reception units.
Furthermore, by providing such a polarization rotator at one end of the polarization maintaining optical fiber, a general-purpose polarization maintaining optical fiber is used for a portion other than the polarization rotator, and the bidirectional light of the above aspect is used. Since the transmission device can be configured, the manufacturing cost can be reduced and the maintainability can be improved.

また、上記態様に係る双方向光伝送装置が、前記偏波保持光ファイバを複数備え、前記第１の光導波路素子は、前記第１の基板上に配設された複数の前記第１の送受信ユニットを有し、前記第２の光導波路素子は、前記第２の基板上に配設された複数の前記第２の送受信ユニットを有し、複数の前記偏波保持光ファイバは、複数の前記第１の送受信ユニットと、複数の前記第２の送受信ユニットと、を各別に接続し、複数の前記偏波保持光ファイバ同士が並列して一体化されていてもよい。   The bidirectional optical transmission apparatus according to the above aspect includes a plurality of the polarization maintaining optical fibers, and the first optical waveguide element includes a plurality of the first transmission / reception devices disposed on the first substrate. The second optical waveguide element includes a plurality of the second transmission / reception units disposed on the second substrate, and the plurality of polarization maintaining optical fibers include the plurality of the polarization maintaining optical fibers. The first transmission / reception unit and the plurality of second transmission / reception units may be connected separately, and the plurality of polarization maintaining optical fibers may be integrated in parallel.

この場合、複数の送受信ユニットの構成を共通化しつつ、複数の送受信ユニットを各別に接続する複数の偏波保持光ファイバが並列して一体化されていることで、設置性に優れ、かつ大容量の通信を行える双方向光伝送装置を提供することができる。   In this case, the configuration of the plurality of transmission / reception units is made common, and the plurality of polarization-maintaining optical fibers that connect the plurality of transmission / reception units separately are integrated in parallel, so that the installation is excellent and the capacity is high. It is possible to provide a bidirectional optical transmission apparatus capable of performing the above communication.

また、本発明の第２態様に係る偏波保持光ファイバは、第１の光導波路素子に接続される第１の端部と、第２の光導波路素子に接続される第２の端部と、光波の電界面の向きを変換する偏波回転部と、を備える偏波保持光ファイバであって、前記偏波回転部から出射する光波の電界面の向きが、前記偏波回転部に入射する光波の電界面の向きに略直交し、前記第１の端部は、前記第１の光導波路素子に対する前記第１の端部における前記偏波保持光ファイバのスロー軸の方向を規制する第１のコネクタキーを備え、前記第２の端部は、前記第２の光導波路素子に対する前記第２の端部における前記偏波保持光ファイバのスロー軸の方向を、前記第１の光導波路素子に対する前記第１の端部における前記偏波保持光ファイバのスロー軸の方向に対して略直交する方向に規制する第２のコネクタキーを備える。   Moreover, the polarization maintaining optical fiber according to the second aspect of the present invention includes a first end connected to the first optical waveguide element, and a second end connected to the second optical waveguide element. A polarization maintaining optical fiber comprising: a polarization rotation unit that converts a direction of an electric field surface of a light wave, wherein the direction of the electric field surface of the light wave emitted from the polarization rotation unit is incident on the polarization rotation unit The first end portion restricts a direction of a slow axis of the polarization maintaining optical fiber at the first end portion with respect to the first optical waveguide element. 1 connector key, and the second end portion indicates the direction of the slow axis of the polarization maintaining optical fiber at the second end portion with respect to the second optical waveguide device, and the first optical waveguide device In the direction of the slow axis of the polarization maintaining optical fiber at the first end with respect to A second connector key to regulate in a direction substantially orthogonal to.

上記態様に係る偏波保持光ファイバは、光波の電界面の向きを変換する偏波回転部を備えている。さらに、偏波保持光ファイバの両端部には、第１の光導波路素子に対する第１の端部における偏波保持光ファイバのスロー軸の方向と、第２の光導波路素子に対する前記第２の端部における偏波保持光ファイバのスロー軸の方向と、を互いに略直交させる第１および第２のコネクタキーが備えられている。このため、偏波保持光ファイバの両端部を第１および第２の光導波路素子に接続し、第１および第２の光導波路素子が電界面の向きが互いに同一な光波を出射した場合、第１および第２の光導波路素子に入射する光波の電界面の向きが同一となる。これにより、第１および第２の光送信部が同一の電界面の向きを有する光波を出射し、かつ第１および第２の光受信部に同一の電界面の向きを有する光波が入射する。以上により、第１および第２の送受信ユニットの構成を共通化することができる。   The polarization maintaining optical fiber according to the above aspect includes a polarization rotation unit that converts the direction of the electric field surface of the light wave. Furthermore, at both ends of the polarization maintaining optical fiber, the direction of the slow axis of the polarization maintaining optical fiber at the first end with respect to the first optical waveguide element and the second end with respect to the second optical waveguide element There are provided first and second connector keys that make the direction of the slow axis of the polarization maintaining optical fiber in the section substantially orthogonal to each other. Therefore, when both ends of the polarization maintaining optical fiber are connected to the first and second optical waveguide elements, and the first and second optical waveguide elements emit light waves having the same electric field plane direction, The direction of the electric field surface of the light wave incident on the first and second optical waveguide elements is the same. As a result, the first and second optical transmitters emit light waves having the same electric field plane direction, and light waves having the same electric field plane direction are incident on the first and second optical receiver units. As described above, the configurations of the first and second transmission / reception units can be shared.

本発明の上記態様によれば、双方向光伝送装置に用いられる一対の送受信ユニットの構成を共通化することができる。   According to the above aspect of the present invention, the configuration of the pair of transmission / reception units used in the bidirectional optical transmission apparatus can be shared.

第１実施形態に係る双方向光伝送装置の構成を示す図である。It is a figure which shows the structure of the bidirectional | two-way optical transmission apparatus which concerns on 1st Embodiment. 図１の偏波合分波部の構成を示す図である。It is a figure which shows the structure of the polarization multiplexing / demultiplexing part of FIG. 図１の偏波保持光ファイバおよび偏波回転部の構成を示す図である。It is a figure which shows the structure of the polarization maintaining optical fiber and polarization rotation part of FIG. 図３の偏波保持光ファイバおよび偏波回転部の変形例を示す図である。It is a figure which shows the modification of the polarization maintaining optical fiber and polarization rotation part of FIG. 第２実施形態に係る双方向光伝送装置の構成を示す図である。It is a figure which shows the structure of the bidirectional | two-way optical transmission apparatus which concerns on 2nd Embodiment. 図５の偏波保持光ファイバおよび偏波回転部の構成を示す図である。It is a figure which shows the structure of the polarization maintaining optical fiber and polarization rotation part of FIG. 第３実施形態に係る双方向光伝送装置の構成を示す図である。It is a figure which shows the structure of the bidirectional | two-way optical transmission apparatus which concerns on 3rd Embodiment. 偏波保持マルチコア光ファイバを本実施形態に用いた場合の構成例を示す図である。It is a figure which shows the structural example at the time of using a polarization maintaining multi-core optical fiber for this embodiment.

（第１実施形態）
第１実施形態に係る双方向光伝送装置の構成を、図１を参照しながら以下に説明する。
図１に示すように、双方向光伝送装置１０は光導波路素子（第１の光導波路素子）１ａ、光導波路素子（第２の光導波路素子）１ｂ、および偏波保持光ファイバ６を備える。 (First embodiment)
The configuration of the bidirectional optical transmission apparatus according to the first embodiment will be described below with reference to FIG.
As shown in FIG. 1, the bidirectional optical transmission device 10 includes an optical waveguide element (first optical waveguide element) 1 a, an optical waveguide element (second optical waveguide element) 1 b, and a polarization maintaining optical fiber 6.

また図１に示すように、光導波路素子（基板型光導波路素子）１ａは、基板（第１の基板）２ａ、光送信部（第１の光送信部）３ａ、光受信部（第１の光受信部）４ａ、および偏波合分波部（第１の偏波合分波部）５ａを備える。光導波路素子（基板型光導波路素子）１ｂは、基板（第２の基板）２ｂ、光送信部（第２の光送信部）３ｂ、光受信部（第２の光受信部）４ｂ、および偏波合分波部（第２の偏波合分波部）５ｂを備える。   As shown in FIG. 1, an optical waveguide element (substrate-type optical waveguide element) 1a includes a substrate (first substrate) 2a, an optical transmitter (first optical transmitter) 3a, and an optical receiver (first optical transmitter). An optical receiving unit) 4a and a polarization multiplexing / demultiplexing unit (first polarization multiplexing / demultiplexing unit) 5a. An optical waveguide element (substrate-type optical waveguide element) 1b includes a substrate (second substrate) 2b, an optical transmission unit (second optical transmission unit) 3b, an optical reception unit (second optical reception unit) 4b, and a polarization A multiplexing / demultiplexing unit (second polarization multiplexing / demultiplexing unit) 5b is provided.

光導波路素子１ａ、１ｂとしては、例えばＳｉｌｉｃｏｎ ｏｎ Ｉｎｓｕｌａｔｏｒ（ＳＯＩ）基板を用いた素子が挙げられる。また、インジウムリン（ＩｎＰ）基板上に光導波路が形成されていてもよい。
光導波路素子１ａ、１ｂとしてＳＯＩ基板を用いる場合には、アンドープＳｉで形成され、平面を有する基板２ａ、２ｂを用いる。基板２ａ、２ｂ上に例えば３μｍ程度の厚みを有する不図示のＳｉＯ２で形成されるＢｕｒｉｅｄ Ｏｘｉｄｅ（ＢＯＸ）層である下クラッドと、その上部にＳＯＩ層により作製されるＳｉのコア及びたとえばその上部にＳｉＯ２で形成した上クラッドからなるＳｉ導波路を作製することができる。
ここで、基板２ａ、２ｂは互いに同一の基板を用いているが、これに限定されず、基板２ａ、２ｂは互いに異なる基板を用いてもよい。
Ｓｉ導波路は、矩形の導波路及びリブ型の導波路を基本構造とした方向性結合器などの各要素デバイスを構成し、基板２ａ、２ｂ上で各要素デバイスがそれぞれ接続される。これにより、１チップ（１素子）上に集積デバイスを形成することができる。 Examples of the optical waveguide elements 1a and 1b include elements using a silicon on insulator (SOI) substrate. An optical waveguide may be formed on an indium phosphide (InP) substrate.
When an SOI substrate is used as the optical waveguide elements 1a and 1b, substrates 2a and 2b made of undoped Si and having a flat surface are used. A lower clad that is a buried oxide (BOX) layer formed of SiO 2 (not shown) having a thickness of, for example, about 3 μm on the substrates 2a and 2b, a Si core formed by an SOI layer on the upper clad, and an upper portion thereof, for example A Si waveguide made of an upper clad formed of SiO 2 can be produced.
Here, the same substrates are used as the substrates 2a and 2b, but the present invention is not limited to this, and the substrates 2a and 2b may be different substrates.
The Si waveguide constitutes each element device such as a directional coupler having a rectangular waveguide and a rib-type waveguide as a basic structure, and each element device is connected on the substrates 2a and 2b. Thereby, an integrated device can be formed on one chip (one element).

光送信部３ａ、３ｂとしては、例えばインジウムリン（ＩｎＰ）系の材料で構成されたＬａｓｅｒ Ｄｉｏｄｅ（ＬＤ）を用いることができる。
光送信部３ａ、３ｂは、基板２ａ、２ｂ上にそれぞれ実装されている。光送信部３ａ、３ｂとしてＩｎＰ系のＬＤを用いることで間接遷移型バンドギャップを持ち非発光なデバイスであるシリコンを導波路として使用するとともに、１チップ上に送受信に必要な光部品も集積することができる。
光送信部３ａ、３ｂは、偏光された光波を出射する。図示の例では、光送信部３ａ、３ｂはＴＥモードの光波を出射している。ＴＥモードの光波は、主電界の向きが基板２ａ、２ｂの平面に平行である。
また、光送信部３ａ、３ｂとしてＬＤを用いる場合、ＬＤと光導波路との接続部には、ＬＤの持つ大きなモードフィールド径に合せるために、モードコンバータを利用することもできる。これにより損失を低減することができる。
なお、光送信部３ａ、３ｂは基板２ａ、２ｂ上に実装されていなくてもよく、例えば基板２ａ、２ｂの外部にＬＤを配設して、このＬＤから基板２ａ、２ｂに対して光を入力してもよい。この場合には、基板２ａ、２ｂ上に配設された各入力端を、光送信部３ａ、３ｂとみなすことができる。
なお、共通化の観点から、例えば光導波路素子１ａの外部にＬＤが配設される場合は、光導波路素子１ｂについても外部にＬＤが配設されるように構成することが好ましい。 As the optical transmitters 3a and 3b, for example, a laser diode (LD) made of an indium phosphide (InP) material can be used.
The optical transmitters 3a and 3b are mounted on the substrates 2a and 2b, respectively. By using InP-based LDs as the optical transmitters 3a and 3b, silicon that is a non-light emitting device having an indirect transition type band gap is used as a waveguide, and optical components necessary for transmission and reception are also integrated on one chip. be able to.
The optical transmitters 3a and 3b emit polarized light waves. In the illustrated example, the optical transmitters 3a and 3b emit TE-mode light waves. In the TE mode light wave, the direction of the main electric field is parallel to the plane of the substrates 2a and 2b.
In addition, when an LD is used as the optical transmitters 3a and 3b, a mode converter can be used at the connection between the LD and the optical waveguide in order to match the large mode field diameter of the LD. Thereby, loss can be reduced.
The optical transmitters 3a and 3b may not be mounted on the substrates 2a and 2b. For example, an LD is disposed outside the substrates 2a and 2b, and light is transmitted from the LD to the substrates 2a and 2b. You may enter. In this case, each input end disposed on the substrates 2a and 2b can be regarded as the optical transmitters 3a and 3b.
From the viewpoint of sharing, for example, when an LD is disposed outside the optical waveguide element 1a, it is preferable that the LD be disposed outside the optical waveguide element 1b.

ここで、本発明において、ＴＥモードとは、光導波路素子１ａ、１ｂにおいて主電界が基板２ａ、２ｂに対して水平となるモードの事を指す。また、本実施形態において、ＴＭモードとは、光導波路素子１ａ、１ｂにおいて主電界が基板２ａ、２ｂに対して垂直となるモードの事を指す。なお、上記のＴＥモードとは厳密には光の進行方向に対して電界が垂直方向にのみ存在するモードのことを指し、光導波路素子１ａ、１ｂにおいては厳密なＴＥモードとはならないが、本実施形態ではこれもＴＥモードと定義する。   Here, in the present invention, the TE mode refers to a mode in which the main electric field is horizontal to the substrates 2a and 2b in the optical waveguide elements 1a and 1b. In the present embodiment, the TM mode refers to a mode in which the main electric field is perpendicular to the substrates 2a and 2b in the optical waveguide elements 1a and 1b. The above-mentioned TE mode refers to a mode in which an electric field exists only in a direction perpendicular to the traveling direction of light, and the optical waveguide elements 1a and 1b are not strict TE modes. In the embodiment, this is also defined as a TE mode.

また、偏波合分波部５ａ、５ｂと偏波保持光ファイバ６との接続においては、ＴＥ及びＴＭの二つのモードの主電界の向きが直交（略直交）することから、偏波保持光ファイバ６の両端部のうち、一方を偏波保持光ファイバ６のスロー軸方向に、他方を上記のスロー軸と直交（略直交）するファスト軸方向に合うように偏波保持光ファイバ６と偏波合分波部５ａ、５ｂとを接続することが可能である。
また、ファイバとの接続において、基板側のＴＥモードの主電界の向きと、偏波保持ファイバのスローまたはファスト軸の意図した方向とを合わせて接続する際には、０度で接続することが望ましいが、ここで、この角度は０°に限定されず、双方向光伝送装置１０が正常に機能する範囲内でずれが生じてもよい。その場合、この角度が具体的には−１０°〜＋１０°をなす範囲で、偏波保持光ファイバ６と偏波合分波部５ａ、５ｂとを接続することが好ましい。
なお、本実施形態における「略直交」とは、光波が光導波路素子１ａ、１ｂ内に伝達された際にＴＥモード若しくはＴＭモードとして正常に機能する範囲をいう。すなわち、「略直交」とは厳密に９０°を指す概念ではなく、例えば９０°±１０°であればよい。 In addition, in the connection between the polarization multiplexing / demultiplexing units 5a and 5b and the polarization maintaining optical fiber 6, the directions of the main electric fields of the two modes of TE and TM are orthogonal (substantially orthogonal). Of the both ends of the fiber 6, one is aligned with the polarization maintaining optical fiber 6 so that one is aligned with the slow axis direction of the polarization maintaining optical fiber 6 and the other is aligned with the fast axis direction orthogonal (substantially orthogonal) to the slow axis. It is possible to connect the multiplexing / demultiplexing units 5a and 5b.
In addition, when connecting the fiber together with the direction of the main electric field of the TE mode on the substrate side and the intended direction of the slow or fast axis of the polarization maintaining fiber, the connection can be made at 0 degree. Although this is desirable, this angle is not limited to 0 °, and a deviation may occur within a range in which the bidirectional optical transmission device 10 functions normally. In that case, it is preferable that the polarization maintaining optical fiber 6 and the polarization multiplexing / demultiplexing portions 5a and 5b are connected within a range in which this angle specifically forms −10 ° to + 10 °.
Note that “substantially orthogonal” in the present embodiment refers to a range that functions normally as a TE mode or a TM mode when a light wave is transmitted into the optical waveguide elements 1a and 1b. That is, “substantially orthogonal” does not strictly indicate 90 °, and may be 90 ° ± 10 °, for example.

また、データを光に変換する場合、光送信部３ａ、３ｂに直接又は光送信部３ａ、３ｂと偏波合分波部５ａ、５ｂとの間に不図示の変調器を設けてもよい。
この場合、変調器としてリング共振器や、マッハツェンダ型光変調器などの、基板２ａ、２ｂ上に実装可能な変調器を利用することができる。特に高速動作に適した変調としてキャリアプラズマ効果を利用した変調が挙げられる。この場合、Ｓｉが半導体であることを利用して、イオン注入によりｐｎ接合を形成し、電圧を印加することによりキャリアの濃度を変化させることで、変調器を伝播する光の位相を変調することができる。このような変調器は通常、導波路の持つ二つの直交する偏光を持つ導波モードの内、片方のモードに合わせて設計され、異なる偏波面に対応するためには、設計を変える必要がある。 Further, when data is converted into light, a modulator (not shown) may be provided in the optical transmitters 3a and 3b directly or between the optical transmitters 3a and 3b and the polarization multiplexing / demultiplexing units 5a and 5b.
In this case, a modulator that can be mounted on the substrates 2a and 2b, such as a ring resonator and a Mach-Zehnder optical modulator, can be used as the modulator. In particular, modulation utilizing the carrier plasma effect can be cited as modulation suitable for high-speed operation. In this case, using the fact that Si is a semiconductor, a pn junction is formed by ion implantation, and the phase of light propagating through the modulator is modulated by changing the carrier concentration by applying a voltage. Can do. Such a modulator is usually designed for one of the two waveguide modes with two orthogonal polarizations of the waveguide, and the design needs to be changed to accommodate different polarization planes. .

光受信部４ａ、４ｂとしては、例えばＰｈｏｔｏ Ｄｅｔｅｃｔｏｒ（ＰＤ）素子を用いることができる。また、基板２ａ、２ｂ上にゲルマニウム（Ｇｅ）を成長させたＧｅＰＤを利用してもよい。ＰＤについては、両偏波を同時に受信できる形状はあるが、通常はそれぞれの偏波に対して異なる特性をもつことから、受信感度を最大化するなど、特性面から各偏波に応じた設計が望ましい。
光受信部４ａ、４ｂは、基板２ａ、２ｂ上にそれぞれ実装されている。
なお、光受信部４ａ、４ｂは基板２ａ、２ｂ上に実装せずに基板２ａ、２ｂの外部に実装して、基板２ａ、２ｂの外部で光を受信することもできる。なお、この場合、基板上の、光信号が外部へ出力される出力端を光受信部とみなすことができる。
なお、共通化の観点から、例えば光導波路素子１ａの外部にＰＤ等が配設される場合は、光導波路素子１ｂについても外部にＰＤ等が配設されるように構成することが好ましい。 As the optical receivers 4a and 4b, for example, a Photo Detector (PD) element can be used. Alternatively, GePD in which germanium (Ge) is grown on the substrates 2a and 2b may be used. PD has a shape that can receive both polarizations at the same time, but usually it has different characteristics for each polarization, so it is designed according to each polarization in terms of characteristics, such as maximizing reception sensitivity. Is desirable.
The optical receivers 4a and 4b are mounted on the substrates 2a and 2b, respectively.
The light receiving units 4a and 4b can be mounted outside the substrates 2a and 2b without being mounted on the substrates 2a and 2b, and can receive light outside the substrates 2a and 2b. In this case, an output terminal on the substrate from which an optical signal is output to the outside can be regarded as an optical receiver.
From the viewpoint of sharing, for example, when a PD or the like is disposed outside the optical waveguide element 1a, it is preferable that the optical waveguide element 1b is also configured such that the PD or the like is disposed outside.

偏波合分波部５ａ、５ｂは、異なる偏波状態の光波を分波および合波可能である。偏波合分波部５ａは、光送信部３ａおよび光受信部４ａに対して光導波路により接続されている。偏波合分波部５ｂは、光送信部３ｂおよび光受信部４ｂに対して光導波路により接続されている。偏波合分波部５ａ、５ｂには、例えば方向性結合器を用いることができる。
方向性結合器では、導波路のＴＥモードとＴＭモードとの間に実効屈折率差があることを利用して、異なるビート長を持ち、片方の偏波のみを選択的に遷移させることが可能である。 The polarization multiplexing / demultiplexing units 5a and 5b can demultiplex and multiplex light waves having different polarization states. The polarization multiplexing / demultiplexing unit 5a is connected to the optical transmission unit 3a and the optical reception unit 4a by an optical waveguide. The polarization multiplexing / demultiplexing unit 5b is connected to the optical transmission unit 3b and the optical reception unit 4b by an optical waveguide. For the polarization multiplexing / demultiplexing units 5a and 5b, for example, directional couplers can be used.
With a directional coupler, it is possible to selectively transition only one polarization with different beat lengths by utilizing the difference in effective refractive index between the TE mode and TM mode of the waveguide. It is.

図２は偏波合分波部５ａ、５ｂに方向性結合器５０を用いた場合の概念図である。図２に示すように、偏波合分波部５ａ、５ｂは、光導波路５１、５２を有する。光導波路５１は、第１のポート５１ａと、曲がり導波路５１ｂと、直線導波路５１ｃと、曲がり導波路５１ｄと、第３のポート５１ｅと、を有する。光導波路５２は、第２のポート５２ａと、曲がり導波路５２ｂと、直線導波路５２ｃと、を有する。ここで、方向性結合器５０および光導波路５１、５２では、矩形形状のシリコン導波路から不連続な断面を有することなく連続的に各導波路と接続されることが可能である。
第１のポート５１ａは、光送信部３ａ若しくは光送信部３ｂに接続されている。第２のポート５２ａは、光受信部４ａ若しくは光受信部４ｂに接続されている。第３のポート５１ｅは、偏波保持光ファイバ６に接続されている。 FIG. 2 is a conceptual diagram when the directional coupler 50 is used in the polarization multiplexing / demultiplexing units 5a and 5b. As shown in FIG. 2, the polarization multiplexing / demultiplexing units 5 a and 5 b have optical waveguides 51 and 52. The optical waveguide 51 includes a first port 51a, a bent waveguide 51b, a straight waveguide 51c, a bent waveguide 51d, and a third port 51e. The optical waveguide 52 has a second port 52a, a bent waveguide 52b, and a straight waveguide 52c. Here, the directional coupler 50 and the optical waveguides 51 and 52 can be continuously connected to each waveguide without having a discontinuous cross section from the rectangular silicon waveguide.
The first port 51a is connected to the optical transmitter 3a or the optical transmitter 3b. The second port 52a is connected to the optical receiver 4a or the optical receiver 4b. The third port 51 e is connected to the polarization maintaining optical fiber 6.

光導波路５１、５２は、第１のポート５１ａ及び第２のポート５２ａから直線導波路５１ｃおよび直線導波路５２ｃに向かって、曲がり導波路５１ｂ、５２ｂによって互いになだらかに接近するように曲げられる。直線導波路５１ｃおよび直線導波路５２ｃは、光が選択的に遷移可能な所定の間隔を空けて互いに平行に配置され、方向性結合器５０を構成する。そして光導波路５１は、曲がり導波路５１ｄによって光導波路５２から第３のポート５１ｅ近傍までなだらかに離れる方向に曲げられ偏波保持光ファイバ６に接続される。一方、光導波路５２は光導波路５１からなだらかに離れる方向に曲げられて終端される。   The optical waveguides 51 and 52 are bent so as to approach each other gently by the bent waveguides 51b and 52b from the first port 51a and the second port 52a toward the straight waveguide 51c and the straight waveguide 52c. The straight waveguide 51 c and the straight waveguide 52 c are arranged in parallel to each other with a predetermined interval at which light can selectively transition, and constitute the directional coupler 50. The optical waveguide 51 is bent by a bent waveguide 51d so as to be gently separated from the optical waveguide 52 to the vicinity of the third port 51e and connected to the polarization maintaining optical fiber 6. On the other hand, the optical waveguide 52 is bent in a direction away from the optical waveguide 51 and terminated.

第１のポート５１ａには、光送信部３ａ若しくは光送信部３ｂが出射したＴＥモードの光波が入射する。第１のポート５１ａから入射したＴＥモードの光波は、曲がり導波路５１ｂを通過し、光導波路５２に遷移することなく、直線導波路５１ｃ、曲がり導波路５１ｄ、および第３のポート５１ｅを介して、偏波保持光ファイバ６内に進入する。
一方、第３のポート５１ｅには、偏波保持光ファイバ６内をＴＥモードの光波の進行方向と逆方向に進行するＴＭモードの光波が入射する。第３のポート５１ｅに入射したＴＭモードの光波は、曲がり導波路５１ｄを通過し、方向性結合器５０内で直線導波路５１ｃから直線導波路５２ｃに遷移する。直線導波路５２ｃに遷移されたＴＭモードの光波は曲がり導波路５２ｂに進入する。曲がり導波路５２ｂに進入したＴＭモードの光波は、第２のポート５２ａを介して、光受信部４ａ若しくは光受信部４ｂに入射する。
つまり、光導波路５１において、第３のポート５１ｅから直線導波路５１ｃの途中にかけて、ＴＭモードとＴＥモードとの２種類のモードの光波が共存する。
なお、第３のポート５１ｅと偏波保持光ファイバ６との間には、モードフィールド径を調整するために不図示のモードコンバータが配置されてもよい。 The TE mode light wave emitted from the optical transmitter 3a or the optical transmitter 3b is incident on the first port 51a. The TE-mode light wave incident from the first port 51a passes through the curved waveguide 51b and passes through the straight waveguide 51c, the curved waveguide 51d, and the third port 51e without transitioning to the optical waveguide 52. Then, the light enters the polarization maintaining optical fiber 6.
On the other hand, a TM mode light wave traveling in the direction opposite to the traveling direction of the TE mode light wave in the polarization maintaining optical fiber 6 is incident on the third port 51e. The TM mode light wave incident on the third port 51 e passes through the curved waveguide 51 d and transits from the straight waveguide 51 c to the straight waveguide 52 c in the directional coupler 50. The TM mode light wave transitioned to the straight waveguide 52c bends and enters the waveguide 52b. The TM mode light wave that has entered the bent waveguide 52b enters the optical receiver 4a or the optical receiver 4b via the second port 52a.
That is, in the optical waveguide 51, light waves of two types of modes, TM mode and TE mode, coexist from the third port 51e to the middle of the straight waveguide 51c.
A mode converter (not shown) may be disposed between the third port 51e and the polarization maintaining optical fiber 6 in order to adjust the mode field diameter.

なお、光導波路の場合、ＴＥモードの方が実効屈折率が高いため、ＴＭモードの方が他方に遷移しやすい。そのため、図２では、光導波路５１を伝播するＴＭモードの光波が光導波路５２に遷移するように構成される。しかしながら、方向性結合器は、図２の構成に限定されず、使用する光送信部及び光受信部の種類に対応するように適宜設計可能である。例えば実行屈折率の条件を調整して、光導波路５１を伝播するＴＥモードの光波が光導波路５２に遷移するように構成してもよい。その場合、第３のポート５１ｅにはＴＥモードの光波が入射し、光導波路５１を伝播するように構成される。
また、図２では光導波路５１、５２の両方がそれぞれ曲がり導波路を有するが、光導波路５１、５２の一方のみに曲がり導波路を設けて方向性結合器５０を構成してもよい。 In the case of an optical waveguide, since the effective refractive index is higher in the TE mode, the TM mode is easier to transition to the other. Therefore, in FIG. 2, a TM mode light wave propagating through the optical waveguide 51 is configured to transition to the optical waveguide 52. However, the directional coupler is not limited to the configuration shown in FIG. 2 and can be appropriately designed so as to correspond to the types of the optical transmitter and the optical receiver used. For example, the effective refractive index condition may be adjusted so that a TE mode light wave propagating through the optical waveguide 51 transitions to the optical waveguide 52. In that case, a TE mode light wave is incident on the third port 51 e and propagates through the optical waveguide 51.
In FIG. 2, both of the optical waveguides 51 and 52 each have a curved waveguide, but the directional coupler 50 may be configured by providing a curved waveguide only in one of the optical waveguides 51 and 52.

図３に示すように、偏波保持光ファイバ６は、コア６ａと、一対の応力付与部６ｂと、クラッド６ｃとで構成される光ファイバ本体部６ｄと、コネクタキー（第１のコネクタキー）６５ａと、コネクタキー（第２のコネクタキー）６５ｂと、を備える。光ファイバ本体部６ｄ内には、図３に示すようにコア６ａと、一対の応力付与部６ｂと、クラッド６ｃとが長手方向の全長に亘って延在している。
コア６ａの両端部は、不図示の接続部を介して、それぞれ偏波合分波部５ａ、５ｂの第３のポート５１ｅに光学的に接続される。コネクタキー６５ａ、６５ｂは、偏波保持光ファイバ６の両端部に配設されている。コネクタキー６５ａ、６５ｂはそれぞれ、フェルール６３、シース６４、及びキー部６５で構成される。フェルール６３はジルコニアなどのセラミクスや金属等で形成され、クラッド６ｃの外周を覆っている。シース６４は、金属等で形成され、空間Ｓを介してフェルール６３の外周を囲むように形成される。キー部６５ａ、６５ｂは、シース６４の外周面から径方向の外側に向けて突出している。キー部６５ａ、６５ｂは、光導波路素子１ａ、１ｂの接続部が備える不図示のキー溝と係合して、基板２ａ、２ｂに対する偏波保持光ファイバ６の両端部におけるスロー軸の向きをそれぞれ規制する。
なお、図示例の偏波保持光ファイバ６は、応力付与部６ｂが略円形の断面を有するＰＡＮＤＡ形光ファイバであるが、他の種類の偏波保持光ファイバ、例えばボウタイ形光ファイバや、楕円コア形光ファイバも使用可能である。 As shown in FIG. 3, the polarization-maintaining optical fiber 6 includes an optical fiber main body 6d composed of a core 6a, a pair of stress applying portions 6b, and a clad 6c, and a connector key (first connector key). 65a and a connector key (second connector key) 65b. In the optical fiber main body 6d, as shown in FIG. 3, a core 6a, a pair of stress applying portions 6b, and a clad 6c extend over the entire length in the longitudinal direction.
Both end portions of the core 6a are optically connected to the third ports 51e of the polarization multiplexing / demultiplexing portions 5a and 5b, respectively, via connection portions (not shown). The connector keys 65 a and 65 b are disposed at both ends of the polarization maintaining optical fiber 6. Each of the connector keys 65a and 65b includes a ferrule 63, a sheath 64, and a key portion 65. The ferrule 63 is made of ceramics such as zirconia, metal or the like, and covers the outer periphery of the clad 6c. The sheath 64 is made of metal or the like, and is formed so as to surround the outer periphery of the ferrule 63 through the space S. The key portions 65a and 65b protrude outward from the outer peripheral surface of the sheath 64 in the radial direction. The key portions 65a and 65b are engaged with key grooves (not shown) provided in the connection portions of the optical waveguide elements 1a and 1b, and the directions of the slow axes at both ends of the polarization maintaining optical fiber 6 with respect to the substrates 2a and 2b are respectively set. regulate.
The polarization maintaining optical fiber 6 in the illustrated example is a PANDA optical fiber in which the stress applying portion 6b has a substantially circular cross section, but other types of polarization maintaining optical fibers, such as a bow tie optical fiber, an elliptical optical fiber, etc. A core-type optical fiber can also be used.

ここで本実施形態の偏波保持光ファイバ６は、図１および図３に示すように、光波の電界面の向きを変換する偏波回転部７を備えている。偏波回転部７は、偏波保持光ファイバ６の光ファイバ本体部６ｄに配設されている。本実施形態における偏波回転部７は、偏波保持光ファイバ６（光ファイバ本体部６ｄ）を軸方向にねじることで形成されている。これにより、偏波回転部７から出射する光波の電界面の向きが、偏波回転部７に入射する光波の電界面の向きに対して略直交する。
図１に示す例では、光導波路素子１ａから出射したＴＥモードの光波は、偏波回転部７でＴＭモードの光波に変換されて光導波路素子１ｂに入射する。また、光導波路素子１ｂから出射したＴＥモードの光波は、偏波回転部７でＴＭモードの光波に変換されて光導波路素子１ａに入射する。 Here, the polarization maintaining optical fiber 6 of the present embodiment includes a polarization rotation unit 7 that converts the direction of the electric field surface of the light wave, as shown in FIGS. 1 and 3. The polarization rotation unit 7 is disposed in the optical fiber main body 6 d of the polarization maintaining optical fiber 6. The polarization rotation unit 7 in the present embodiment is formed by twisting the polarization maintaining optical fiber 6 (optical fiber main body 6d) in the axial direction. Thereby, the direction of the electric field surface of the light wave emitted from the polarization rotation unit 7 is substantially orthogonal to the direction of the electric field surface of the light wave incident on the polarization rotation unit 7.
In the example shown in FIG. 1, a TE mode light wave emitted from the optical waveguide element 1a is converted into a TM mode light wave by the polarization rotation unit 7 and enters the optical waveguide element 1b. The TE mode light wave emitted from the optical waveguide element 1b is converted into a TM mode light wave by the polarization rotation unit 7 and is incident on the optical waveguide element 1a.

また、図３に示すように、キーリング６１のコネクタキー６５ａは、光ファイバ６の一方の端部における外周面のうち、スロー軸上に配設されている。キーリング６２のコネクタキー６５ｂは、光ファイバ６の他方の端部における外周面のうち、ファスト軸上に配設されている。これにより、コネクタキー６５ａ、６５ｂは、光導波路素子１ａとの接続部における基板２ａに対する光ファイバ６のスロー軸の方向と、光導波路素子１ｂとの接続部における基板２ｂに対する光ファイバ６のスロー軸の方向と、を互いに略直交させる。   As shown in FIG. 3, the connector key 65 a of the key ring 61 is disposed on the slow shaft on the outer peripheral surface at one end of the optical fiber 6. The connector key 65 b of the key ring 62 is disposed on the fast axis in the outer peripheral surface at the other end of the optical fiber 6. Thus, the connector keys 65a and 65b are connected to the optical fiber 6 in the connecting portion with the optical waveguide element 1a in the direction of the slow axis of the optical fiber 6 and in the connecting portion with the optical waveguide element 1b. These directions are substantially orthogonal to each other.

以上説明したように、本実施形態の双方向光伝送装置１０によれば、光導波路素子１ａとの接続部における偏波保持光ファイバ６の基板２ａに対するスロー軸の向きと、光導波路素子１ｂとの接続部における偏波保持光ファイバ６の基板２ｂに対するスロー軸の向きと、が互いに略直交する。このため、光送信部３ａがＴＥモードの光波を出射すると、光受信部４ｂに入射する光波はＴＭモードとなる。
また、光送信部３ｂがＴＥモードの光波を出射すると、光受信部４ａに入射する光波はＴＭモードとなる。このように、光送信部３ａおよび光送信部３ｂが出射する光波の電界面の向きを共通にしつつ、光受信部４ａおよび光受信部４ｂに入射する光波の電界面の向きを共通にすることができる。
これにより、光送信部３ａおよび光送信部３ｂを共通化し、かつ光受信部４ａおよび光受信部４ｂを共通化できるため、光導波路素子１ａおよび光導波路素子１ｂの構成のうち、送受信ユニットの構成を共通化することが可能となる。従って、比較的簡易な構成で双方向光伝送装置を実現することができ、製造コストの低減、及びメンテナンス性の向上を実現できる。
なお、本実施形態において、送受信ユニットとは、図１の構成のうち、光送信部３ａ、光受信部４ａ、および偏波合分波部５ａ、もしくは、光送信部３ｂ、光受信部４ｂ、および偏波合分波部５ｂのいずれかの構成を有するものとする。
また、本実施形態では、基板２ａ及び２ｂに同一の基板を用いれば光導波路素子１ａおよび光導波路素子１ｂの構成を共通化することも可能となる。従って、本実施形態を用いることで、比較的簡易な構成で双方向光伝送装置を実現することができる。また、基板２ａ、２ｂには同一の基板を使用するため、基板２ａ、２ｂ上に同一の送受信ユニットを作製すれば、共通の光導波路素子１ａおよび光導波路素子１ｂを容易に製造することが可能となる。また、製造コストの低減、及びメンテナンス性の向上を実現できる。 As described above, according to the bidirectional optical transmission device 10 of the present embodiment, the direction of the slow axis with respect to the substrate 2a of the polarization maintaining optical fiber 6 at the connection portion with the optical waveguide element 1a, the optical waveguide element 1b, The direction of the slow axis with respect to the substrate 2b of the polarization-maintaining optical fiber 6 at the connection portion is substantially orthogonal to each other. For this reason, when the light transmission unit 3a emits a TE mode light wave, the light wave incident on the light reception unit 4b becomes the TM mode.
In addition, when the light transmission unit 3b emits a TE mode light wave, the light wave incident on the light reception unit 4a becomes the TM mode. As described above, the direction of the electric field surface of the light wave emitted from the optical transmission unit 3a and the optical transmission unit 3b is made common, and the direction of the electric field surface of the light wave incident on the light reception unit 4a and the light reception unit 4b is made common. Can do.
Thereby, since the optical transmitter 3a and the optical transmitter 3b can be shared and the optical receiver 4a and the optical receiver 4b can be shared, the configuration of the transmission / reception unit among the configurations of the optical waveguide element 1a and the optical waveguide element 1b. Can be made common. Therefore, the bidirectional optical transmission apparatus can be realized with a relatively simple configuration, and the manufacturing cost can be reduced and the maintainability can be improved.
In the present embodiment, the transmission / reception unit refers to the optical transmission unit 3a, the optical reception unit 4a, and the polarization multiplexing / demultiplexing unit 5a, or the optical transmission unit 3b, the optical reception unit 4b in the configuration of FIG. And the polarization multiplexing / demultiplexing unit 5b.
In the present embodiment, if the same substrate is used as the substrates 2a and 2b, the configuration of the optical waveguide element 1a and the optical waveguide element 1b can be made common. Therefore, by using this embodiment, a bidirectional optical transmission apparatus can be realized with a relatively simple configuration. Further, since the same substrate is used for the substrates 2a and 2b, if the same transmission / reception unit is manufactured on the substrates 2a and 2b, the common optical waveguide element 1a and the optical waveguide element 1b can be easily manufactured. It becomes. Further, it is possible to realize a reduction in manufacturing cost and an improvement in maintainability.

また、光導波路素子１ａと光導波路素子１ｂとの間で光ファイバ本体部６ｄが軸方向にねじられることで、このねじられた部分の前後におけるスロー軸の向きを互いに略直交させることができる。
これにより、光導波路素子１ａとの接続部における偏波保持光ファイバ６の基板２ａに対するスロー軸の向きと、光導波路素子１ｂとの接続部における偏波保持光ファイバ６の基板２ｂに対するスロー軸の向きとが互いに略直交する構成を、比較的簡易な構成の双方向光伝送装置で実現することができる。 Further, the optical fiber body 6d is twisted in the axial direction between the optical waveguide element 1a and the optical waveguide element 1b, so that the directions of the slow axes before and after the twisted portion can be made substantially orthogonal to each other.
Thereby, the direction of the slow axis with respect to the substrate 2a of the polarization-maintaining optical fiber 6 at the connection portion with the optical waveguide element 1a, and the slow axis with respect to the substrate 2b of the polarization-maintaining optical fiber 6 at the connection portion with the optical waveguide element 1b. A configuration in which the directions are substantially orthogonal to each other can be realized by a bidirectional optical transmission device having a relatively simple configuration.

また、本実施形態の偏波保持光ファイバ６によれば、その両端部の間に配設された偏波回転部７が、光波の電界面の向きを変換する。さらに、偏波保持光ファイバ６の両端部には、光導波路素子１ａとの接続部における基板２ａに対する偏波保持光ファイバ６のスロー軸の方向と、光導波路素子１ｂとの接続部における基板２ｂに対する偏波保持光ファイバのスロー軸の方向と、を互いに略直交させるコネクタキー６５ａ、６５ｂが備えられている。
このため、偏波保持光ファイバ６の両端部を光導波路素子１ａ、１ｂに接続し、光送信部３ａ、３ｂが電界面の向きが互いに同一な光波を出射した場合、光受信部４ａ、４ｂに入射する光波の電界面の向きが同一となる。これにより、光送信部３ａ、３ｂが同一の電界面の向きを有する光波を出射し、かつ光受信部４ａ、４ｂに同一の電界面の向きを有する光波が入射する。
以上により、光送信部３ａおよび光送信部３ｂを共通化し、かつ光受信部４ａおよび光受信部４ｂを共通化できるため、光導波路素子１ａおよび光導波路素子１ｂの構成のうち、送受信ユニットの構成を共通化することが可能となる。従って、比較的簡易な構成で双方向光伝送装置を実現することができ、製造コストの低減、及びメンテナンス性の向上を実現できる。
また、本実施形態では、基板２ａ及び２ｂに同一の基板を用いれば光導波路素子１ａおよび光導波路素子１ｂの構成を共通化することも可能となる。従って、本実施形態を用いることで、比較的簡易な構成で双方向光伝送装置を実現することができる。また、基板２ａ、２ｂには同一の基板を使用するため、基板２ａ、２ｂ上に同一の送受信ユニットを作製すれば、共通の光導波路素子１ａおよび光導波路素子１ｂを容易に製造することが可能となる。また、製造コストの低減、及びメンテナンス性の向上を実現できる。このように、本実施形態の偏波保持光ファイバ６を用いることで、双方向光伝送装置１０の構成の簡易化を容易に実現することができる。 In addition, according to the polarization maintaining optical fiber 6 of the present embodiment, the polarization rotation unit 7 disposed between the both ends converts the direction of the electric field surface of the light wave. Further, at both ends of the polarization maintaining optical fiber 6, the direction of the slow axis of the polarization maintaining optical fiber 6 with respect to the substrate 2a at the connection portion with the optical waveguide element 1a and the substrate 2b at the connection portion with the optical waveguide element 1b are provided. Connector keys 65a and 65b are provided to make the direction of the slow axis of the polarization maintaining optical fiber substantially perpendicular to each other.
For this reason, when both ends of the polarization-maintaining optical fiber 6 are connected to the optical waveguide elements 1a and 1b, and the optical transmitters 3a and 3b emit light waves having the same electric field plane direction, the optical receivers 4a and 4b The direction of the electric field surface of the light wave incident on the same is the same. As a result, the light transmitting units 3a and 3b emit light waves having the same electric field surface direction, and light waves having the same electric field surface direction are incident on the light receiving units 4a and 4b.
As described above, since the optical transmission unit 3a and the optical transmission unit 3b can be shared and the optical reception unit 4a and the optical reception unit 4b can be shared, the configuration of the transmission / reception unit among the configurations of the optical waveguide element 1a and the optical waveguide element 1b. Can be made common. Therefore, the bidirectional optical transmission apparatus can be realized with a relatively simple configuration, and the manufacturing cost can be reduced and the maintainability can be improved.
In the present embodiment, if the same substrate is used as the substrates 2a and 2b, the configuration of the optical waveguide element 1a and the optical waveguide element 1b can be made common. Therefore, by using this embodiment, a bidirectional optical transmission apparatus can be realized with a relatively simple configuration. Further, since the same substrate is used for the substrates 2a and 2b, if the same transmission / reception unit is manufactured on the substrates 2a and 2b, the common optical waveguide element 1a and the optical waveguide element 1b can be easily manufactured. It becomes. Further, it is possible to realize a reduction in manufacturing cost and an improvement in maintainability. Thus, by using the polarization maintaining optical fiber 6 of the present embodiment, the configuration of the bidirectional optical transmission device 10 can be easily simplified.

なお、偏波保持光ファイバ６は、偏波回転部７として、図４に示すような偏波回転素子７Ａを有していてもよい。この偏波回転素子７Ａは、光波の電界面の向きを９０°回転可能であり、偏波保持光ファイバ６の一方の端部に配設されている。偏波回転素子７Ａの一方の端部には、コネクタキー６５ａ若しくは６５ｂと係合するキー溝７ｂが形成されている。偏波回転素子７Ａのキー溝７ｂが形成されている端部は、偏波保持光ファイバ６に光学的に接続される。偏波回転素子７Ａの他方の端部には、キーリング６１、６２と同様のコネクタキー７ｃが形成されている。偏波保持光ファイバ６と偏波回転素子７Ａとは、コネクタキー６５ａ若しくは６５ｂと、キー溝７ｂと、によりスロー軸の方向が一致した状態で連結される。偏波回転素子７Ａのコネクタキー７ｃが形成されている側の端部は、光導波路素子１ａ若しくは１ｂに光学的に接続される。
なお、偏波回転素子７Ａは、偏波保持光ファイバ６の一方の端部に装着されていてもよい。あるいは、偏波回転素子７Ａは、偏波保持光ファイバ６と一体に形成されていてもよい。 The polarization maintaining optical fiber 6 may have a polarization rotation element 7A as shown in FIG. This polarization rotation element 7A can rotate the direction of the electric field surface of the light wave by 90 °, and is disposed at one end of the polarization maintaining optical fiber 6. A key groove 7b that engages with the connector key 65a or 65b is formed at one end of the polarization rotation element 7A. The end of the polarization rotation element 7 </ b> A where the key groove 7 b is formed is optically connected to the polarization maintaining optical fiber 6. A connector key 7c similar to the key rings 61 and 62 is formed at the other end of the polarization rotation element 7A. The polarization maintaining optical fiber 6 and the polarization rotation element 7A are connected to each other in a state in which the directions of the slow axes coincide with each other by the connector key 65a or 65b and the key groove 7b. The end of the polarization rotation element 7A on the side where the connector key 7c is formed is optically connected to the optical waveguide element 1a or 1b.
The polarization rotation element 7A may be attached to one end of the polarization maintaining optical fiber 6. Alternatively, the polarization rotation element 7A may be formed integrally with the polarization maintaining optical fiber 6.

つまり、本実施形態では、偏波保持光ファイバ６の一方の先端部に偏波回転素子７Ａを付加する構成をとる。これにより、汎用の偏波保持光ファイバ６をねじらずに実質的に偏波保持光ファイバ６の基板２ａに対するスロー軸の向きと、偏波保持光ファイバ６の基板２ｂに対するスロー軸の向きとを互いに略直交する構成を実現する事が可能となる。したがって、汎用の偏波保持光ファイバ６をそのまま使用できる為、両端のコネクタキーの向きが互いに９０度異なった短尺ファイバなどの特殊ファイバが不要となる。また、このことから、故障時及び配線引き直し時などにおいて、偏波保持光ファイバ６を光導波路素子１ａ、１ｂに接続する作業が容易となる等、メンテナンス性に優れた双方向光伝送装置１０を実現する事が可能となる。   That is, in this embodiment, the polarization rotation element 7A is added to one tip of the polarization maintaining optical fiber 6. Accordingly, the orientation of the slow axis with respect to the substrate 2a of the polarization maintaining optical fiber 6 and the orientation of the slow axis with respect to the substrate 2b of the polarization maintaining optical fiber 6 are substantially reduced without twisting the general-purpose polarization maintaining optical fiber 6. It is possible to realize a configuration substantially orthogonal to each other. Therefore, since the general-purpose polarization maintaining optical fiber 6 can be used as it is, a special fiber such as a short fiber in which the directions of the connector keys at both ends are different from each other by 90 degrees is not necessary. In addition, this makes it easy to connect the polarization-maintaining optical fiber 6 to the optical waveguide elements 1a and 1b in the event of a failure or when the wiring is redrawn. Can be realized.

（第２実施形態）
次に、本発明に係る第２実施形態について説明するが、第１実施形態と基本的な構成は同様である。このため、同様の構成には同一の符号を付してその説明は省略し、異なる点についてのみ説明する。
本実施形態では、光導波路素子１ａ、１ｂが複数の送受信ユニットを備えている点が第１実施形態と異なる。 (Second Embodiment)
Next, a second embodiment according to the present invention will be described. The basic configuration is the same as that of the first embodiment. For this reason, the same code | symbol is attached | subjected to the same structure, the description is abbreviate | omitted, and only a different point is demonstrated.
This embodiment is different from the first embodiment in that the optical waveguide elements 1a and 1b include a plurality of transmission / reception units.

図５に示すように、本実施形態の双方向光伝送装置２０は、光導波路素子１ａ、１ｂと、複数の偏波保持光ファイバ６と、偏波回転部７と、を備える。
光導波路素子１ａは、基板２ａおよび基板２ａ上に配設された複数の送受信ユニット（第１の送受信ユニット）８ａ〜８ｃを備える。送受信ユニット８ａ〜８ｃはそれぞれ、光送信部３ａ、光受信部４ａ、および偏波合分波部５ａを有する。各送受信ユニット８ａ〜８ｃの構成要素は互いに同一であるため、送受信ユニット８ａ〜８ｃは互いに同一である。
光導波路素子１ｂは、基板２ｂおよび基板２ｂ上に配設された複数の送受信ユニット（第２の送受信ユニット）８ｄ〜８ｆを備える。送受信ユニット８ｄ〜８ｆはそれぞれ、光送信部３ｂ、光受信部４ｂ、および偏波合分波部５ｂを有する。各送受信ユニット８ｄ〜８ｆの構成要素は互いに同一であるため、送受信ユニット８ｄ〜８ｆは互いに同一である。
なお、図５では、一つの偏波回転部７が３本の偏波保持光ファイバ６に対して、一直線状に延在しているが、これは、後述する図６について、３本の偏波保持光ファイバ６それぞれにおいて９０度ねじった箇所３つが、偏波保持光ファイバ６の長手方向に対して垂直方向にそれぞれ並列して配置されている構造を示している。ここで、偏波回転部７は、前述した構造に限定されず、例えば、３本の偏波保持光ファイバそれぞれにおいて９０度ねじった箇所３つが、偏波保持光ファイバ６の長手方向に対して垂直方向にそれぞれ並列して配置されていなくてもよい。 As shown in FIG. 5, the bidirectional optical transmission device 20 of the present embodiment includes optical waveguide elements 1 a and 1 b, a plurality of polarization maintaining optical fibers 6, and a polarization rotation unit 7.
The optical waveguide element 1a includes a substrate 2a and a plurality of transmission / reception units (first transmission / reception units) 8a to 8c disposed on the substrate 2a. Each of the transmission / reception units 8a to 8c includes an optical transmission unit 3a, an optical reception unit 4a, and a polarization multiplexing / demultiplexing unit 5a. Since the components of each of the transmission / reception units 8a to 8c are the same as each other, the transmission / reception units 8a to 8c are the same.
The optical waveguide element 1b includes a substrate 2b and a plurality of transmission / reception units (second transmission / reception units) 8d to 8f disposed on the substrate 2b. Each of the transmission / reception units 8d to 8f includes an optical transmission unit 3b, an optical reception unit 4b, and a polarization multiplexing / demultiplexing unit 5b. Since the constituent elements of the transmission / reception units 8d to 8f are the same as each other, the transmission / reception units 8d to 8f are the same.
In FIG. 5, one polarization rotator 7 extends in a straight line with respect to the three polarization-maintaining optical fibers 6, but this is because three polarization rotators 7 in FIG. 3 shows a structure in which three portions twisted by 90 degrees in each of the wave holding optical fibers 6 are arranged in parallel in the direction perpendicular to the longitudinal direction of the polarization holding optical fiber 6. Here, the polarization rotation unit 7 is not limited to the structure described above, and for example, three portions twisted by 90 degrees in each of the three polarization maintaining optical fibers are in the longitudinal direction of the polarization maintaining optical fiber 6. They do not have to be arranged in parallel in the vertical direction.

図５に示すように、複数の偏波保持光ファイバ６はそれぞれ、送受信ユニット８ａ〜８ｃと、送受信ユニット８ｄ〜８ｆと、を各別に接続している。   As shown in FIG. 5, the plurality of polarization maintaining optical fibers 6 respectively connect the transmission / reception units 8a to 8c and the transmission / reception units 8d to 8f.

図６は、図５に示す複数の偏波保持光ファイバ６の説明図である。図６に示すように、複数の偏波保持光ファイバ６はそれぞれ、両端部の間でねじれた状態で並列して一体化されている。複数の偏波保持光ファイバ６同士を一体化する方法としては、樹脂固定によるファイバ同士の接着、固定や図６に示すようにテープ１１で固定することで、両端をテープ化してもよい。
複数の偏波保持光ファイバ６を並列して一体化する場合、例えば、ファイバ同士を一体化する前にそれぞれの偏波保持光ファイバ６の先端部を一度、図６に対し、上方向に引き出して、光ファイバの軸回りに９０度ねじることが好ましい。そして、ねじれを保った状態で先端部を、上方向に引き出される前の位置と同等の位置まで戻し、それぞれのファイバ同士を並列して一体化する。このように引き出してねじることで偏波回転部７を確実に形成することができる。 FIG. 6 is an explanatory diagram of a plurality of polarization maintaining optical fibers 6 shown in FIG. As shown in FIG. 6, each of the plurality of polarization maintaining optical fibers 6 is integrated in parallel while being twisted between both ends. As a method of integrating a plurality of polarization maintaining optical fibers 6, both ends may be formed into a tape by bonding or fixing the fibers by resin fixing or fixing with a tape 11 as shown in FIG. 6.
When integrating a plurality of polarization-maintaining optical fibers 6 in parallel, for example, before integrating the fibers, the tip of each polarization-maintaining optical fiber 6 is once pulled upward with respect to FIG. Thus, it is preferable to twist 90 degrees around the axis of the optical fiber. Then, with the twist kept, the tip is returned to a position equivalent to the position before being pulled upward, and the respective fibers are integrated in parallel. Thus, the polarization rotation part 7 can be formed reliably by pulling out and twisting.

また、偏波保持光ファイバ６を引き出すことなく、並列された状態でねじって偏波回転部７を形成してもよい。
なお、偏波回転部７に代えて、図４に示すような偏波回転素子７Ａを一方の端部に備えた複数の偏波保持光ファイバ６を、並列して一体化してもよい。 Further, the polarization rotation unit 7 may be formed by twisting in a parallel state without pulling out the polarization maintaining optical fiber 6.
Instead of the polarization rotator 7, a plurality of polarization maintaining optical fibers 6 each having a polarization rotator 7A as shown in FIG. 4 at one end may be integrated in parallel.

本実施形態の双方向光伝送装置２０によれば、複数の送受信ユニット８ａ〜８ｆの構成を共通化しつつ、複数の送受信ユニット８ａ〜８ｆを各別に接続する複数の偏波保持光ファイバ６が並列して一体化されていることで、設置性に優れ、かつ大容量の通信を行える双方向光伝送装置２０を提供することができる。
なお、本実施形態では、光導波路素子１ａ、１ｂがそれぞれ３つの送受信ユニットを備えている場合を例示しているが、これに限定されない。光導波路素子１ａ、１ｂがそれぞれ２つの送受信ユニットを備え、２本の偏波保持光ファイバ６で接続されていてもよいし、光導波路素子１ａ、１ｂがそれぞれ４つ以上の送受信ユニットを備え、４本以上の偏波保持光ファイバ６で接続されていてもよい。 According to the bidirectional optical transmission apparatus 20 of the present embodiment, a plurality of polarization maintaining optical fibers 6 that connect the plurality of transmission / reception units 8a to 8f separately are arranged in parallel while sharing the configuration of the plurality of transmission / reception units 8a to 8f. Thus, the bidirectional optical transmission device 20 that is excellent in installability and capable of performing large-capacity communication can be provided.
In addition, in this embodiment, although the case where the optical waveguide elements 1a and 1b are each provided with three transmission / reception units is illustrated, it is not limited to this. Each of the optical waveguide elements 1a and 1b may include two transmission / reception units, and may be connected by two polarization maintaining optical fibers 6, or each of the optical waveguide elements 1a and 1b may include four or more transmission / reception units, Four or more polarization maintaining optical fibers 6 may be connected.

（第３実施形態）
次に、本発明に係る第３実施形態について説明するが、第１実施形態と基本的な構成は同様である。このため、同様の構成には同一の符号を付してその説明は省略し、異なる点についてのみ説明する。
本実施形態の双方向光伝送装置３０は、図７に示すように、光導波路素子１ａ、１ｂが偏波ローテータ９ａ、９ｂを備えている点が第１実施形態と異なる。 (Third embodiment)
Next, a third embodiment according to the present invention will be described. The basic configuration is the same as that of the first embodiment. For this reason, the same code | symbol is attached | subjected to the same structure, the description is abbreviate | omitted, and only a different point is demonstrated.
As shown in FIG. 7, the bidirectional optical transmission apparatus 30 according to the present embodiment is different from the first embodiment in that the optical waveguide elements 1a and 1b include polarization rotators 9a and 9b.

偏波ローテータ９ａ、９ｂは、光波の電界面の向きを変換する。偏波ローテータ９ａ、９ｂとしては、例えば国際公開第２０１４／２０７９４９号に記載されているように、シリコン導波路に対して２段階の高さを持つ構造を有する偏波変換素子を用いることができる。図７に示すように、偏波ローテータ９ａは偏波合分波部５ａおよび光受信部４ａに接続されている。偏波ローテータ９ｂは偏波合分波部５ｂおよび光受信部４ｂに接続されている。偏波合分波部５ａ、５ｂから出射されたＴＭモードの光波は、偏波ローテータ９ａ若しくは９ｂによりＴＥモードに変換され、光受信部４ａ若しくは４ｂに入射する。   The polarization rotators 9a and 9b convert the direction of the electric field surface of the light wave. As the polarization rotators 9a and 9b, for example, as described in International Publication No. 2014/207949, a polarization conversion element having a structure having a two-stage height with respect to the silicon waveguide can be used. . As shown in FIG. 7, the polarization rotator 9a is connected to the polarization multiplexing / demultiplexing unit 5a and the optical receiving unit 4a. The polarization rotator 9b is connected to the polarization multiplexing / demultiplexing unit 5b and the optical receiving unit 4b. The TM mode light waves emitted from the polarization multiplexing / demultiplexing units 5a and 5b are converted into the TE mode by the polarization rotator 9a or 9b, and enter the light receiving unit 4a or 4b.

本実施形態の双方向光伝送装置３０によれば、例えば光受信部４ａ、４ｂに入射する光波をＴＭモードからＴＥモードに変換することができる。光受信部４ａ、４ｂの受光効率が、ＴＭモードよりＴＥモードの方が高い場合には、本実施形態のように偏波ローテータ９ａ、９ｂを用いることで、この高い受光効率を有するＴＥモードの光波を光受信部４ａ、４ｂに入射させることができる。   According to the bidirectional optical transmission device 30 of the present embodiment, for example, a light wave incident on the optical receivers 4a and 4b can be converted from the TM mode to the TE mode. When the light receiving efficiency of the optical receivers 4a and 4b is higher in the TE mode than in the TM mode, the polarization mode rotators 9a and 9b are used as in the present embodiment, so that the TE mode having the high light receiving efficiency can be obtained. Light waves can be incident on the optical receivers 4a and 4b.

なお、本発明の技術的範囲は前記実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。   The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

例えば、前述した第１〜３実施形態では、コネクタキー６５ａ、６５ｂはシース６４の外周面から径方向の外側に向けて突出していたが、本発明はこれに限られない。例えば、シース６４の外周面から径方向の内側に向けて窪む凹部をコネクタキー６５ａ、６５ｂとしてもよい。この場合、光導波路素子１ａ、１ｂは、凹部であるコネクタキー６５ａ、６５ｂと係合して基板２ａ、２ｂに対するスロー軸の向きを規制する凸部を備えていてもよい。   For example, in the first to third embodiments described above, the connector keys 65a and 65b protrude outward from the outer peripheral surface of the sheath 64 in the radial direction, but the present invention is not limited to this. For example, recesses that are recessed from the outer peripheral surface of the sheath 64 toward the inside in the radial direction may be used as the connector keys 65a and 65b. In this case, the optical waveguide elements 1a and 1b may include convex portions that engage with the connector keys 65a and 65b, which are concave portions, to regulate the direction of the slow shaft with respect to the substrates 2a and 2b.

また、前述した第１〜３実施形態では、偏波保持光ファイバ６をねじることで偏波回転部７を形成していたが、本発明はこれに限られない。例えば、偏波ローテータ９ａ、９ｂを偏波回転部７として用いてもよい。
また、前述した第１〜３実施形態では、偏波保持光ファイバ６の両端部間に偏波回転部７を配設したが、本発明はこれに限られない。例えば、偏波回転部７を偏波保持光ファイバ６の一方の端部と、この端部に接続される光導波路素子と、の間に配設してもよい。 In the first to third embodiments described above, the polarization rotation unit 7 is formed by twisting the polarization maintaining optical fiber 6, but the present invention is not limited to this. For example, the polarization rotators 9 a and 9 b may be used as the polarization rotation unit 7.
In the first to third embodiments described above, the polarization rotation unit 7 is disposed between both end portions of the polarization maintaining optical fiber 6, but the present invention is not limited to this. For example, the polarization rotation unit 7 may be disposed between one end of the polarization maintaining optical fiber 6 and an optical waveguide element connected to this end.

また、前述した第１〜３実施形態では、シングルコアの偏波保持光ファイバ６を用いて偏波回転部７を形成していたが、本発明はこれに限られず偏波保持マルチコア光ファイバ６Ａを用いてもよい。
この場合、送信側（第１の光導波路素子）と受信側（第２の光導波路素子）とで共通の光導波路素子を用いるためには図８に示すようなコアで構成することが好ましい。つまり、光ファイバ６Ａが光ファイバ６Ａの軸回りに９０°回転された場合に、対応する位置にそれぞれコアが存在するように４つのコア６ａ１〜６ａ４が配置され、さらに送信側の光波がすべて同一の偏波状態を有するように構成することが好ましい。このようにコア６ａ１〜６ａ４を配置することで偏波保持マルチコア光ファイバを用いた場合でも本発明を適用でき、受信側と送信側とで共通の光導波路素子を用いることができる。
また、偏波保持マルチコア光ファイバ６Ａを、例えば、図５に示すような複数の送受信ユニット同士を光接続するために用いた場合、隣接した送受信ユニット間において偏波合分波部で分波された導波路を伝播する光の偏波モードが隣同士で異なるように構成される。そのため、隣接した送受信ユニット間におけるクロストークの影響を低減できる。このため、隣接した送受信ユニット同士をより近距離に配置することが可能である。
なお、図８において、応力付与部については記載を省略している。また、図８ではコアの数が４個の場合を示しているが光ファイバ６Ａが９０°回転された場合に対応する位置にそれぞれコアが存在するように構成されていれば、コアの数が８個や１２個など、４の倍数であればよい。
また、偏波保持マルチコア光ファイバにおける偏波保持方向については、図８のように全てのコアに対して同一方向にスロー軸が配置されている構造のほかに、図８の偏波保持光ファイバ６Ａの断面構造において、偏波保持光ファイバ６Ａの軸回り方向に延在する偏波保持光ファイバ６Ａの外形に沿った方向に、それぞれのコアにおけるスロー軸が配置され、偏波保持光ファイバ６Ａの径方向に、それぞれのコアにおけるファスト軸が配置されている構造が挙げられる。 In the first to third embodiments described above, the polarization rotation unit 7 is formed using the single-core polarization-maintaining optical fiber 6. However, the present invention is not limited to this, and the polarization-maintaining multi-core optical fiber 6A. May be used.
In this case, in order to use a common optical waveguide element on the transmission side (first optical waveguide element) and the reception side (second optical waveguide element), it is preferable to use a core as shown in FIG. That is, when the optical fiber 6A is rotated by 90 ° around the axis of the optical fiber 6A, the four cores 6a1 to 6a4 are arranged so that the cores are respectively present at the corresponding positions, and the light waves on the transmission side are all the same. It is preferable to configure so as to have the following polarization state. By arranging the cores 6a1 to 6a4 in this way, the present invention can be applied even when a polarization maintaining multicore optical fiber is used, and a common optical waveguide element can be used on the reception side and the transmission side.
Further, when the polarization maintaining multi-core optical fiber 6A is used for optically connecting a plurality of transmission / reception units as shown in FIG. 5, for example, the polarization multiplexing / demultiplexing unit demultiplexes between adjacent transmission / reception units. The polarization modes of light propagating through the waveguide are configured to be different from each other. Therefore, the influence of crosstalk between adjacent transmission / reception units can be reduced. For this reason, it is possible to arrange adjacent transmission / reception units at a closer distance.
In addition, in FIG. 8, description is abbreviate | omitted about the stress provision part. FIG. 8 shows the case where the number of cores is four. However, if the cores are configured to exist at positions corresponding to the case where the optical fiber 6A is rotated by 90 °, the number of cores is It may be a multiple of 4, such as 8 or 12.
Further, with respect to the polarization maintaining direction in the polarization maintaining multi-core optical fiber, in addition to the structure in which the slow axis is arranged in the same direction with respect to all the cores as shown in FIG. 8, the polarization maintaining optical fiber of FIG. In the cross-sectional structure of 6A, the slow axes in the respective cores are arranged in the direction along the outer shape of the polarization maintaining optical fiber 6A extending in the direction around the axis of the polarization maintaining optical fiber 6A. The structure in which the fast axis in each core is arranged in the radial direction of each is mentioned.

その他、本発明の趣旨を逸脱しない範囲で、上記した実施の形態における構成要素を周知の構成要素に置き換えることは適宜可能であり、また、上記した実施形態や変形例を適宜組み合わせてもよい。   In addition, the constituent elements in the above-described embodiment can be appropriately replaced with known constituent elements without departing from the gist of the present invention, and the above-described embodiments and modifications may be appropriately combined.

１ａ、１ｂ…光導波路素子、２ａ、２ｂ…基板、３ａ、３ｂ…光送信部、４ａ、４ｂ…光受信部、５ａ、５ｂ…偏波合分波部、６…偏波保持光ファイバ、６５ａ、６５ｂ…コネクタキー、７…偏波回転部、７Ａ…偏波回転素子（偏波回転部）、１０、２０、３０…双方向光伝送装置   DESCRIPTION OF SYMBOLS 1a, 1b ... Optical waveguide element, 2a, 2b ... Board | substrate, 3a, 3b ... Optical transmission part, 4a, 4b ... Optical receiving part, 5a, 5b ... Polarization multiplexing / demultiplexing part, 6 ... Polarization holding optical fiber, 65a , 65b... Connector key, 7... Polarization rotation unit, 7A... Polarization rotation element (polarization rotation unit) 10, 20, 30.

Claims (5)

第１の光送信部と、第１の光受信部と、前記第１の光送信部及び前記第１の光受信部に接続され、異なる偏波状態の光波を分波および合波可能な第１の偏波合分波部と、を有する第１の送受信ユニットが第１の基板上に配設された第１の光導波路素子と、
第２の光送信部と、第２の光受信部と、前記第２の光送信部及び前記第２の光受信部に接続され、異なる偏波状態の光波を分波および合波可能な第２の偏波合分波部と、を有する第２の送受信ユニットが第２の基板上に配設された第２の光導波路素子と、
前記第１の光導波路素子と前記第２の光導波路素子とを接続する偏波保持光ファイバと、を備え、
前記第１の光導波路素子と前記偏波保持光ファイバとの接続部における前記偏波保持光ファイバの前記第1の基板に対するスロー軸の向きと、前記第２の光導波路素子と前記偏波保持光ファイバとの接続部における前記偏波保持光ファイバの前記第２の基板に対する前記スロー軸の向きと、が互いに略直交している双方向光伝送装置。 A first optical transmitter, a first optical receiver, a first optical transmitter connected to the first optical transmitter and the first optical receiver, and capable of demultiplexing and multiplexing optical waves of different polarization states A first optical waveguide element in which a first transmission / reception unit having a polarization multiplexing / demultiplexing unit is disposed on a first substrate;
A second optical transmitter, a second optical receiver, and a second optical transmitter connected to the second optical transmitter and the second optical receiver and capable of demultiplexing and multiplexing optical waves of different polarization states A second optical waveguide element in which a second transmission / reception unit having two polarization multiplexing / demultiplexing units is disposed on a second substrate;
A polarization maintaining optical fiber connecting the first optical waveguide element and the second optical waveguide element,
The direction of the slow axis of the polarization maintaining optical fiber with respect to the first substrate at the connection between the first optical waveguide element and the polarization maintaining optical fiber, the second optical waveguide element, and the polarization maintaining A bidirectional optical transmission apparatus in which a direction of the slow axis with respect to the second substrate of the polarization maintaining optical fiber at a connection portion with an optical fiber is substantially orthogonal to each other. 前記第１の光導波路素子と前記第２の光導波路素子との間で前記偏波保持光ファイバが軸方向にねじられている、請求項１に記載の双方向光伝送装置。   The bidirectional optical transmission apparatus according to claim 1, wherein the polarization maintaining optical fiber is twisted in an axial direction between the first optical waveguide element and the second optical waveguide element. 前記偏波保持光ファイバは、前記偏波保持光ファイバの一方の端部に配設された、前記光波の電界面の向きを回転可能な偏波回転素子を有する、請求項１に記載の双方向光伝送装置。   The polarization maintaining optical fiber includes a polarization rotator disposed at one end of the polarization maintaining optical fiber and capable of rotating a direction of an electric field surface of the light wave. Opto-optical transmission device. 前記偏波保持光ファイバを複数備え、
前記第１の光導波路素子は、前記第１の基板上に配設された複数の前記第１の送受信ユニットを有し、
前記第２の光導波路素子は、前記第２の基板上に配設された複数の前記第２の送受信ユニットを有し、
複数の前記偏波保持光ファイバは、複数の前記第１の送受信ユニットと、複数の前記第２の送受信ユニットと、を各別に接続し、複数の前記偏波保持光ファイバ同士が並列して一体化されている、請求項１から３のいずれか一項に記載の双方向光伝送装置。 A plurality of the polarization maintaining optical fibers,
The first optical waveguide element has a plurality of the first transmission / reception units disposed on the first substrate,
The second optical waveguide device has a plurality of the second transmission / reception units disposed on the second substrate,
The plurality of polarization maintaining optical fibers are connected to the plurality of first transmission / reception units and the plurality of second transmission / reception units separately, and the plurality of polarization maintaining optical fibers are integrated in parallel. The bidirectional optical transmission apparatus according to claim 1, wherein the bidirectional optical transmission apparatus is configured. 第１の光導波路素子に接続される第１の端部と、第２の光導波路素子に接続される第２の端部と、光波の電界面の向きを変換する偏波回転部と、を備える偏波保持光ファイバであって、
前記偏波回転部から出射する光波の電界面の向きが、前記偏波回転部に入射する光波の電界面の向きに略直交し、
前記第１の端部は、前記第１の光導波路素子に対する前記第１の端部における前記偏波保持光ファイバのスロー軸の方向を規制する第１のコネクタキーを備え、
前記第２の端部は、前記第２の光導波路素子に対する前記第２の端部における前記偏波保持光ファイバのスロー軸の方向を、前記第１の光導波路素子に対する前記第１の端部における前記偏波保持光ファイバのスロー軸の方向に対して略直交する方向に規制する第２のコネクタキーを備える偏波保持光ファイバ。 A first end connected to the first optical waveguide element; a second end connected to the second optical waveguide element; and a polarization rotation part for converting the direction of the electric field surface of the light wave. A polarization maintaining optical fiber comprising:
The direction of the electric field surface of the light wave emitted from the polarization rotation unit is substantially orthogonal to the direction of the electric field surface of the light wave incident on the polarization rotation unit,
The first end includes a first connector key that regulates a direction of a slow axis of the polarization maintaining optical fiber at the first end with respect to the first optical waveguide element;
The second end portion indicates the direction of the slow axis of the polarization maintaining optical fiber at the second end portion with respect to the second optical waveguide element, and the first end portion with respect to the first optical waveguide element. A polarization-maintaining optical fiber comprising a second connector key that regulates in a direction substantially orthogonal to the direction of the slow axis of the polarization-maintaining optical fiber.
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